Nitric oxide inhibits nitrate reductase activity in wheat leaves

• Published in: Plant physiology and biochemistry Vol. 49; no. 2; pp. 124 - 130
• Main Authors: Rosales, Eliana Paola, Iannone, María Florencia, Groppa, María Daniela, Benavides, María Patricia
• Format: Journal Article
• Language: English
• Published: Paris Elsevier Masson SAS 01-02-2011; Elsevier
• Subjects: Biological and medical sciences; Blotting, Western; Enzyme Activation - drug effects; Fundamental and applied biological sciences. Psychology; Immunoprecipitation; Nitrate reductase; Nitrate Reductase - metabolism; Nitrates; Nitrates - metabolism; Nitric oxide; Nitric Oxide - metabolism; Nitrogen metabolism; Nitroprusside - pharmacology; Plant Leaves - drug effects; Plant Leaves - enzymology; Plant Leaves - metabolism; Plant physiology and development; S-Nitrosoglutathione - pharmacology; Triticum - drug effects; Triticum - enzymology; Triticum - metabolism; Triticum aestivum L; NO; Nitrogen metabolism; NR; SNP; Nitrate reductase; Nitric oxide; NiR; Triticum aestivum L; Nitrates; GSNO; Monocotyledones; Enzyme; Plant leaf; Nitrogen; Metabolism; Cereal crop; Enzymatic activity; Plant physiology; Gramineae; Angiospermae; Spermatophyta; Oxidoreductases; Triticum aestivum
• ISSN: 0981-9428; 1873-2690
• DOI: 10.1016/j.plaphy.2010.10.009

Nitrate reductase (NR), a committed enzyme in nitrate assimilation, is involved in the generation of nitric oxide (NO) in plants. In wheat leaf segments exposed to sodium nitroprusside (SNP) or
S-nitrosoglutathione (GSNO), NR activity was significantly reduced to different degrees between 3 and 21 h, whereas its activity was partially recovered when the NO scavenger cPTIO was used. At 21 h, NR activity decreased from 38% with 10 μM SNP to 91% with 500 μM SNP, respect to the C values.
S-nitrosoglutathione reduced NR activity between 18% and 26% only at 3 h. When added directly to the incubation solution, NR activity was quickly and strongly inhibited more than 90% by 10 or 50 μM SNP, whereas 10 μM GSNO reduced the enzyme activity an average of 50%, at 30 min of incubation.
l-NAME and
d-arginine (nitric oxide synthase (NOS) inhibitors) increased NR activity by 14% and 52% respectively, at 21 h of exposure, leading us to suppose that endogenous NOS-dependent NO formation could also be modulating NR activity. NR protein expression was not affected by 10 or 100 μM SNP at 3 or 21 h of incubation, whereas nitration of tyrosines was not detected in the NR protein. Nitrates, which content increased along the time in the tissues, could be exerting a role in this regulation.
► Nitric oxide induced a decrease in nitrate reductase activity in wheat leaf segments. ► Nitrate reductase protein expression was not modified by NO. ► Nitric oxide synthase like enzyme could also be implicated in NO-endogenous formation. ► Regulation of the enzyme activity by NO does not seem to be mediated by Tyr-nitration